1. Field of the Invention
The present invention relates to a print server, printing system, printing method, printing program and computer-readable recording medium on which the printing program is recorded, and more particularly, to a print server, printing system, printing method, printing program and recording medium containing the printing program that perform printing using a plurality of image forming apparatuses in order to increase printing efficiency.
2. Description of the Prior Art
Office work service shops exist that receive print data for a print job from a customer via a recording medium such as a flexible disk or over a network, output such data onto paper using a printer or other type of image forming apparatus, and provide the printed end product to the customer. Where a large number of sheets of paper is to be output at such a shop, the time required for the job may be reduced by performing the printing in a parallel fashion using a plurality of printers. Printing in this manner using a plurality of printers is referred to as cluster printing. In cluster printing, a print server that manages the multiple printers is used. For example, consider a situation in which four printers are connected to a print server, comprising a cluster printing system. When this cluster printing system receives a job that requires printing of 1,000 pages, the job is divided into sections of pages 1-250, pages 251-500, pages 501-750 and pages 751-1000, such that the four printers each perform printing of 250 pages in a parallel fashion. Consequently, the time required for the completion of printing becomes one quarter of the time that would be needed if the entire printing job were performed using a single printer.
However, in the cluster printing system described above, since the printing speed increases in proportion to the number of printers connected, the speed of data transmission from the print server also must increase in accordance with the number of printers. In general, since a printer such as a laser printer cannot stop the printing routine once it is begun and the photoreceptor drum begins to rotate, if the speed of data transmission to the printer is slower than the printing speed, the transmission of image data for one page cannot be completed during the printing of that page, resulting in missing image parts (“data transmission speed” and “printing speed” in this specification refer to the number of pages of image data that can be processed per minute, and PPM (page per minute) is used as the unit of measurement).
In addition, the hard disk, which comprises the image storage device of the print server, has a limited access speed. The effective page throughput of the print server decreases as the image data size increases, and increases as the image data size decreases. For example, in the case of A4-size, full-color image data, the data size is approximately 32 MB after general image compression, and the 32 MB of data must be sent from the print server to the printer within a prescribed period of time in accordance with the printing speed. On the other hand, where the data is monochrome binary data, the compression rate can be increased, and therefore the data size is approximately 200 KB. The data amount that must be sent in the same period of time accordingly becomes 1/160th of that of the full-color image data.
Furthermore, in the cluster printing system described above, where four printers having the same printing speed are connected and A4-size, full-color image data undergoes processing for printing by the four printers simultaneously, for example, since the overall system printing speed increases by a factor of four, simply calculated, the print server must read 128 MB of data (32×4) from the hard disk in a prescribed period of time and send it to the printers.
Therefore, the likelihood of missing image parts increases as the data size and the number of printers connected to the print server increase.
The present invention was made in order to resolve the problems identified above. An object of the present invention is to provide a print server, printing system, printing method, printing program and recording medium containing the printing program in which no missing image parts occur when an image is formed using a plurality of image forming apparatuses.